Solvent paint line flushing cleaners are known to remove un-cured paint from paint application delivery equipment that is used in automotive, furniture and architectural markets. Typically, a solvent cleaner is used for removing a previous paint from the paint spray delivery equipment during a color change cycle by circulating the cleaner through the equipment. This process cleans the previous solvent-based paint color from the paint applicator and prepares it for the next color, thus avoiding color carry over issues. The solvent-based paint being cleaned from the equipment may include epoxy resins, polyether resins, polyacrylate resins, polyurethane resins, polyester resins, melamine resins and combinations of the above resins.
Solvent-based paint line flushing cleaners, also referred to herein as solvent-based purges, have also been used in the industry for several years. These cleaners are typically liquids that are have as the greatest percentage component solvents, sometimes in combination with wax or thickeners. Both 100% solvent and solvent-based purges include volatile organic compounds (VOCs) that readily evaporate into the atmosphere. One negative aspect relating to the use of 100% solvent or solvent-based paint line flushing cleaners has been the generation of VOCs. State and federal laws limit the amount of VOC emissions that can be released into the environment. Each regulated facility must comply with these laws and there is thus a need for low VOC emitting paint line flushing cleaners that provide cleaning benefits comparable to higher VOC paint line flushing cleaners.
The government approach to control VOC emissions has been to exempt certain solvents from the emissions limits as being “VOC-free”. This gives the user the option in some states to subtract the % wt. portion of the exempt solvent from the solvent purge blend resulting in a lower VOC emission per pound of solvent used. The instant invention improves on this approach by actually reducing the total organic solvent used by providing a purging composition that contains more water, which is a not a Volatile Organic Compound (VOC). The resulting solution provides a true reduction in VOC's and a purge that overall is better for the environment.
Cleaners for paint that contain water are known in the art, including water-based alkaline cleaners, water-based solutions of various chemicals dissolved in water and water-based emulsions where water is the continuous phase with a discontinuous organic phase such as solvent.
Water-based alkaline cleaners have been used to remove solvent-based paint from application equipment. Drawbacks of these alkaline cleaners include attack of the paint application delivery equipment and incomplete dissolution of paint. The alkaline cleaners have not shown any sign of actually solvating the paint, which can result in residual paint particles left in the paint lines after purging. As for paint compatibility, the alkaline water-based cleaners leave sufficient amounts of water behind to contaminate the next incoming paint color, which leads to paint defects.
Other water-based coatings removers typically contain mostly water, combined with solvent and optionally surfactant in the form of solutions of solvent in water or emulsions in which the water is the continuous phase and the solvent is the discontinuous phase (oil-in-water emulsion). When applied to a painted or coated substrate, these compositions can soften or dissolve the paint or coating, and bring it to such a condition that it can be removed. The solvents that are typically used include methylene chloride, mineral spirits, toluene, alcohols, acetone, methyl ethyl ketone and N-methylpyrrolidone. One problem with these coatings removers is that many of the solvents that are used are classified as volatile organic compounds (VOC) and as a result their use leads to air emission problems. The present invention provides a solution to this problem.
Solvent-in-water emulsions, that is water continuous emulsions, are easy to make but tend to generate a great deal of foam. These types of emulsions have a water continuous phase and have similar solvency problems dissolving solvent based paint as do water based alkaline cleaning formulas. Most solvent-based paints contain solvents that are not water soluble. When these paints come into contact with water, the paint and water repel each other and the paint tends to fall out of solution and stick inside the application equipments tubing, color changing device and applicator spray cap or bell cup. These residual paint particles result in defects in the new color.
Micro-emulsions are emulsions that appear as translucent clear solutions but have a distinct continuous phase of either water or solvent. It is possible to prepare a thermodynamically stable micro-emulsion with a solvent continuous phase. In order to do this, the system must contain a high percentage of water soluble coupling solvents which increase the cost of the composition and negatively impact the solvating action of the system toward solvent based paint. Micro-emulsions known in the art do not perform as well as the invention described herein in removing or solvating solvent-based paint and are more costly.
With the present invention, a water-in-oil emulsion composition is provided that is useful as a remover for non-aqueous coatings, the use of this remover reduces the amount of volatiles emitted as compared to non-water-in-oil emulsion prior art coatings removers and yet provides desired coating removal properties.